MongoDB is a NoSQL database.
Journal size
MongoDB will create journal files, by default on 64 bit systems, rotating when they hit 1G in size. Apparently it will only create a max of 3G worth of journal files. On my computer (Gentoo Linux) they’re stored in the /var/lib/mongodb/journal directory.
See Journaling and Journaling Administration Notes for more details.
You can reduce the size of journals using the smallfiles configuration option. See Configuration File Options.
